John Baez's old web site has disappeared, presumably since he's no longer associated with the university whose server they were on. In particular his page on the relativistic rocket equations is gone, and that was a useful article for gathering all the equations together.
I was thinking of asking the question What are the equations describing the motion of a relativistic rocket? and posting a tidied up summary of the article as an answer. That way we have a copy in perpetuity (or until the SE goes bust :-).
But we aren't a blog and our mission isn't to save every physics blog that disappears, so I thought I'd check here before posting. If you want to check what I'm talking about a cached copy of the page is temporarily available here. I'd probably omit all the stuff about the fuel.
Opinions please - shall I go ahead?
Ah, it appears the article has not been deleted but has just been moved to this address. Thanks to John Duffield for pointing out its new location.